American Mathematical Society: According to a news report in the June 15, 2006 Nature, it has been established mathematically that soccer goals are contagious, statistically speaking: scoring one goal increases the probability that your team will score more. Michael Hopkin, who write the piece, calls this "one of soccer's classic clichés," and attributes the result to Martin Weigel (Herriot-Watt University, Edinburgh) and his colleagues Elmar Bittner, Andreas Nussbaumer and Wolfhard Janke, all at Leipzig University. The four have posted a preprint on arXiv.org with the title "Football fever: goal distributions and non-Gaussian statistics." As they put it: "modifying the Bernoulli random process underlying the Poissonian model to include a simple component of self-affirmation seems to describe the data surprisingly well and allows to understand the observed deviation from Gaussian statistics." They analyzed "historical football score data from many leagues in Europe as well as from international tournaments, including data from all past tournaments of the 'FIFA World Cup' series" and concluded: "The best fits are found for models where each extra goal encourages a team even more than the previous one: a true sign of football fever." The group paid special attention to three German soccer leagues: the East German Oberliga, the West German Bundesliga and the women's league, the Frauen-Bundesliga. They found that their self-affirmation factor κ was higher for the East German league and highest of all for the women.